52 



AGRICULTURAL CONCLUSIONS. 



The meaning of these results for agricultural 

 practice is essentially the same as their meaning for 

 ecology. If species vary in response to soil aeration 

 it is obvious that the cultural importance of this factor 

 will depend upon the particular crop concerned. Doubt- 

 less certain crops will require very perfect soil aera- 

 tion. Probably others will grow successfully with poor 

 aeration or even with none. As before, detailed applica- 

 tions to practice and theory must await specific knowledge 

 of the aeration responses of the individual crop plants. 

 The relations of crops to temperature and moisture have 

 long been recognized as important and have received con- 

 sideration in practice. To these factors there must now 

 be added the third one of soil aeration and it must be 

 realized that the variations of crops in this regard are 

 as important and probably as wide as they are in regard 

 to temperature and moisture. The present practice of 

 assuming that a maximum of soil aeration is desirable 

 or necessary for all crops is as unsound theoretically 

 and probably as foolish practically as it would be to 

 assume that all crop plants required a maximum of water 

 or the highest possible temperature. Just as each crop 

 has an optimum of water supply and an optimum tempera- 

 ture so it has probably an optimum degree of soil aera- 

 tion. To take account of this in the formulation of an 



